One of the serious challenges the industry faces is developing new gate dielectric materials for DRAM and capacitors. For decades, silicon dioxide (SiO2) was a reliable dielectric. However, as transistors have continued to shrink and the technology has moved from “Full Si” transistor to “Metal Gate/High-k” transistors, the reliability of the SiO2-based gate dielectric is reaching its physical limits. One solution is to use other materials for gate dielectrics, such as hafnium-based or zirconium-based metal oxides. These high-k materials (so-called because of their high dielectric constant) can be made much thicker than SiO2 while achieving the same gate capacitance.
Amino hafnium- and zirconium-containing compounds with substituted cyclopentadienyl ligands have been described. See, e.g. Niinisto et al., Journal of Materials Chemistry (2008), 18(43), 5243-5247; WO2007/066546 to Tri Chemical Laboratories, Inc.; WO2007/140813 to L'Air Liquide Societe Anonyme Pour L'etude et L'exploitation Des Procedes Georges Claude; KR2007-0121281 to DNF Co Ltd; US2008/0102205 to Barry et al.; KR10-2008-0101040 to UP Chemical Co Ltd; and WO2009/036046 to Sigma-Aldrich Co.
The stability of these molecules may result in narrower deposition process windows. Therefore a need remains for novel hafnium- and zirconium-containing precursors.